Variable Stars in Metal-rich Globular Clusters. II. NGC 6316

Abstract

We present time-series VI photometry of the metal-rich globular cluster NGC 6316. Our color-magnitude diagrams show a predominantly red-clump horizontal branch morphology with no evidence of the blue extensions seen in NGC 6388 and NGC 6441. Our data are in good agreement with published estimates of the reddening and metallicity provided the cluster has an absolute distance modulus of 15.5 mag. We have discovered more than one dozen long-period variable stars in our field of view and argue that at least seven of them are members of NGC 6316. We have also discovered four RR Lyrae variables, although only one of them probably belongs to the cluster. The specific frequency of RR Lyrae stars in NGC 6316 is found to be less than 0.4, making it clear that this cluster is a normal, metal-rich globular and is not an analog of NGC 6388 and NGC 6441. We recommend long-term photometric monitoring of NGC 6316 to clarify the nature of the RR Lyrae member candidates, as well as the pulsation classes of the long-period variables.

New LZ and PW(Z) relations of RR Lyrae stars calibrated with Gaia EDR3 parallaxes

“…* Number of RRLs known. References: NGC 3201 (Layden & Sarajedini 2003;Arellano Ferro et al 2014), NGC 4590 (Kains et al 2015), NGC 5824 (Walker et al 2017), NGC 5904 (Oosterhoff 1941;Kaluzny et al 2000;Arellano Ferro et al 2016), NGC 6121 (Yao et al 1988;Kaluzny et al 2013;Stetson et al 2014), NGC 6171 (Dickens 1970;Clement & Shelton 1997;Samus et al 2009;Drake et al 2013), NGC 6316 (Layden et al 2003), NGC 6426 (Grubissich 1958;Papadakis et al 2000;Samus et al 2009), NGC 6569 (Hazen-Liller 1985Soszyński et al 2014) , NGC 6656 (Kunder et al 2013;Soszyński et al 2014), NGC 6864 (Corwin et al 2003;Scott et al 2006), NGC 7006 (Wehlau et al 1999;Samus et al 2009), NGC 7078 (Corwin et al 2008), Rup 106 (Kaluzny et al 1995), Ter 8 (Salinas et al 2005;Torrealba et al 2015)…”

Variable Stars in Metal-Rich Globular Clusters. IV. Long Period Variables in NGC 6496

“…As part of a survey for RR Lyrae stars in metal rich globular clusters (Layden et al 1999(Layden et al , 2003Baker et al 2007), we present multi-band, multi-epoch observations obtained for the metal-rich globular cluster NGC 6496 (C1755-442). This cluster is located at galactic coordinates (l, b) = (348.03 • , -10.01 • ), at a distance ∼11.3 kpc from the Sun.…”